/dev/chat

7:16 AM

Sorry to ask what is such as a basic question but I'm reading about KVM. Wiki states that as of 2007 the KVM (virtual machine) is part of the Linux distribution. So does that mean the main versions of Linux, such as Debian, Ubuntu, RedHat will support this 1 VM

My research is suggesting yes but I've no guarantee that the sources I'm reading are trust worthy

terdon

7:56 AM

@Dave There's no such thing as "the Linux distribution", as you know, there are many, independent and completely separate distributions.

I assume what the article means is either i) many/most main distros include it in their repositories or ii) perhaps the kernel has somehow been tweaked to make it run more smoothly with the virtualization software of kvm.

I do know that I've been running virtualware VMs on Debian and Arch hosts for a few years, with a Windows and Ubuntu guest, so it's not like kvm is the only virtualization solution supported.

Dave

8:20 AM

@terdon, and I assume each VM has i'ts own pros and cons but do you have any opinion in regards to stability?

terdon

@Dave No. I just know I've been using vmware happily on my home machines. I have no experience with VMs on production systems.

The company I work for uses Zen and we've never had an issue. I think (but stress that I don't really know) that it's up to you and a matter of preference. Presumably each solution will have its pros and cons but I'm not the right person to ask. They're all supported by Linux though.

@derobert probably knows about it if he's around.

Or maybe @JennyD.

They're two of our sysadmin types.

Dave

Oh cool. Thanks :)

Faheem Mitha

8:41 AM

I think KVM is an official supported brand of virtual machine. Supported by the Linux kernel.

But that should be easy enough to check. Just read the WP page.

You're in general better off using VMs which the kernel supports, other things being equal.

Yes, en.wikipedia.org/wiki/Kernel-based_Virtual_Machine says KVM has been in the kernel since 2007.

@Dave So all Linux distributions will support it. Unless they're shipping a non-standard kernel.

Jenny D

@terdon You rang?

Yes, KVM is supported.

terdon

@JennyD I just thought you might be able to help @Dave choose a virtualization technology.

Jenny D

My experience is that larger organizations will use VMWare because they're well-known and stable and they have very good automation tools and it's possible to get a good support contract. It feels safe to them.

terdon

Are there certain functions that each excels at or something? Any objective reason to chose one over the other, other than personal preference?

Jenny D

@terdon I've not used Zen or KVM enough to give you a good response to that - I'm a consultant, but most of my work is in larger organizations. I've had good experiences with KVM but not in large settings.

terdon

8:51 AM

Fair enough.

Thanks

Dave

hmmm

this is good reading

@JennyD, so VMWare is actually the 'brand' then?

Jenny D

@Dave Pretty much, yeah. It's got brand awareness at the CTO level, which KVM mostly lacks.

Dave

Oh yes, reading vmware.com/uk

Jenny D

Nobody gets fired for buying VMWare.

Dave

he he , good thing to know

Faheem Mitha

8:54 AM

VMWare is non-free. And it's a paravirtualization thingy or something. Means it grabs and locks up memory.

Dave

@FaheemMitha, does that mean it's different to having deciated memory?

Jenny D

But if you don't need the GUI and the fancy automation tools, I'd say there's really no technical reason to not use KVM instead. Downside is it'll be somewhat harder to find people who know how to manage it, and you have to build some of your own tools (although this may count as an upside for some people :-))

I'm actually using VMWare Fusion on my laptop for my lab environment.

Faheem Mitha

@Dave I don't know what you mean. I would not recommend VMWare, personally.

Jenny D

But if I were running Linux I'd probably use KVM there instead.

Faheem Mitha

It depends what you are trying to do. What are you trying to run?

If it's Linux on Linux, KVM is probably fine.

Jenny D

8:56 AM

Oh, and really really don't go with Virtualbox. Its networking capabilities are less than stellar. It's a toy, not a business product.

Dave

It will be. Our software will have to be written for Linux (well, in C++) to keep it neutral but I also suspect Java will show up soon

Jenny D

In that case, I'd start with KVM. If for some reason it doesn't meet your needs in the future, migration isn't that hard.

(And the reason I don't recommend Zen is that I don't know it well enough to have an opinion.)

Faheem Mitha

@JennyD It's one of the few options if you want to go with a free (as in beer) way of running e.g. Windows on Linux.

Maybe the only one.

Dave

But this is a Big Data solution (I should point out) running with our modules (our hardware and software tool pumps the data in, hardware runs seperatly (obviously) but the software will be on same cluster)

Jenny D

@FaheemMitha I know. I hope it'll develop into something better.

@Dave Sounds like a big setup?

Dave

8:58 AM

So I'm hoping that KVM will be fine if it's stable. not sure if it has any heartbeat functionality or if it can keep the states

@JennyD yes it is, too big for us here (it's being outscourced) but it's important we (I) understand the technologies they're using so I can quizz them etc

Faheem Mitha

@Dave What is heartbeat functionality?

Jenny D

Like I said, I've not seen KVM in very big settings, since the organizations I'm working with tend to go with "what doesn't get the CTO fired" :-)

Dave

Very interesting point @JennyD and thank you so much for taking the time to talk to me:)

Faheem Mitha

I'm sure KVM is fine.

Lots of people use it.

Jenny D

@FaheemMitha That's usually a network protocol other than TCP, such as GRE, which is used to verify that all the nodes in the network are up.

Faheem Mitha

9:01 AM

@JennyD Oh, I see. Ok, thanks.

Dave

Thank you @FaheemMitha for your comments and advice :)

Thank you @terdon for calling them in and also providing your experiences

terdon

You're quite welcome.

Jenny D

@FaheemMitha You can also have heartbeat checks over TCP, but it's useful to have more than one way to check for availability.

@Dave You're welcome! I've enjoyed it :-)

Faheem Mitha

@JennyD Yes, I see.

terdon

I can tell you that we use Zen on a 48-core machine which runs 3-4 VM guests in parallel, two of which run computationally intensive processes pretty much constantly. So, medium size but it seems to be working fine.

Faheem Mitha

9:03 AM

For example, here is what Ramnode uses: ramnode.com/vps.php

So OpenVZ and KVM.

@terdon Zen? You mean Xen?

terdon

Um. yup

Jenny D

Um, I meant Xen to. s/Zen/Xen/g for all I've written today.

Faheem Mitha

@Dave I personally have an OpenVZ Ramnode VPS, fwiw. Though I don't have any idea what OpenVZ is.

Maybe I did once. It's hard to keep these things straight.

There are a lot of different virtualization technologies floating around. Some require you to patch the kernel. Those are usually not great choices because it's extra overhead and fewer people use them.

I once used something called Linux-VServer that falls into that category.

It's still around, but I don't think many people use it. The lead dev is quite friendly, though. Bertl, I think.

Linux-VServer

Linux-VServer is a virtual private server implementation that was created by adding operating system-level virtualization capabilities to the Linux kernel. It is developed and distributed as open-source software. The project was started by Jacques Gélinas. It is now maintained by Herbert Pötzl of Austria and is not related to the Linux Virtual Server project, which implements network load balancing. Linux-VServer is a jail mechanism in that it can be used to securely partition resources on a computer system (such as the file system, CPU time, network addresses and memory) in such a way that processes...

It worked quite well for me while I was using it, but I wouldn't recommend to anyone for the reasons above.

terdon

9:25 AM

@JennyD s/to/too/ too? :P

Jenny D

@terdon Um, that also, yes :-)

Today is a vacation day! I do not need to be albe to splel!

Faheem Mitha

Spelling is overrated. Shakespeare didn't bother with it.

Jenny D

@FaheemMitha It's a fairly modern invention.

Faheem Mitha

@JennyD What, spelling?

Jenny D

@FaheemMitha Yes.

Faheem Mitha

9:40 AM

In English, post Johnson's dictionary, I imagine.

Jenny D

@FaheemMitha I think it had more to do with public schools.

Faheem Mitha

@JennyD Perhaps. I wouldn't know.

Jenny D

@FaheemMitha The dictionary was descriptive, not prescriptive. It described the meaning of the words, it didn't (AFAIK) set a standard of spelling. But when you start teaching all children to read and write, you need school books, and those were prescriptive - not following them was considered an error.

Faheem Mitha

@JennyD I see.

Jenny D

I'm off to do some garden work.

Faheem Mitha

9:57 AM

Take care, @JennyD.

derobert

4:13 PM

0

Q: How do I delete everything on my computer with one command using bash?

I'm trying to delete every single file and directory on my computer. How do I do so?

Answer, obviously, is to use a large enough hammer for that bash.

Faheem Mitha

4:31 PM

@derobert I don't see your answer, though. :-)

Hey, maybe he's a technologically clueless secret agent on the run!

derobert

@FaheemMitha I was tempted to leave an answer featuring cryptsetup luksErase because of course someone who may need to delete everything on his computer on a moment's notice would have full-disk encryption set up to make it easy.

Faheem Mitha

@derobert They would? Why?

derobert

@FaheemMitha well, a secret agent should definitely be prepared!

Faheem Mitha

@derobert Well, they aren't so much about technology. More about murdering people with handguns.

derobert

@FaheemMitha In that case, I guess a bullet through the drive would probably work fairly well...

Faheem Mitha

4:38 PM

Or maybe stealing top secret documents, dunno. I don't know any secret agents, personally.

@derobert Another possible answer. Or taking it out and stomping on it.

derobert

@FaheemMitha And if you did, and told me, you'd have to kill me... so please don't :-P

Faheem Mitha

@derobert :-)

@derobert I notice you haven't attempted my systemd question. Disappointing.

derobert

I have no idea what advantages systemd timers have over cron, other than the obvious ones when your goal is to start a systemd unit

Faheem Mitha

@derobert So you don't use them yourself?

Question: is it worth trying to educate the asker of this insane question?

0

Q: Set apt-get options to tolerate harmless 'dpkg --force-conflicts' kludge?

A conflicting package foo can be made to work with bar, after dpkg --force-conflicts -i foo. But eventually it's time to upgrade, and 'apt-get' objects: % apt-get upgrade Reading package lists... Done Building dependency tree Reading state information... Done You might want to run 'apt-g...

debian apt dpkg

derobert

@FaheemMitha nope, I don't. I use plenty of cron jobs, though.

Faheem Mitha

4:45 PM

@derobert Ok. Did you read the posted answer?

derobert

@FaheemMitha No, I didn't know it had one...

Faheem Mitha

@derobert Someone just posted one today. It isn't terribly coherent, though.

derobert

@FaheemMitha parallel conflicting with moreutils sounds annoying. Maybe one of them should rename (hard, since they're used in scripts) or use alternatives (but that could make for fun scripting...)

I don't think there is a good way to fix it locally, other than rebuilding one of the packages.

@FaheemMitha yeah, that timers answer is rather rambling. A lot of it seems to be you get all the systemd features...

Although, I bet systemd can prevent it from running twice at once—I've certainly had that fun with cron jobs. Something gets fired off every half hour, expected to finish in a second or two. But due to some problem (e.g., NFS mount down) it hangs... by the time you look in to it next morning, cron has spawned 10 of them...

Faheem Mitha

5:03 PM

@derobert But they shouldn't, though. Assuming they are Debian packages.

@derobert Cron can't tell an instance of the same script is already running? I guess not. But systemd can?

derobert

@FaheemMitha They do—check apt-cache show...

@FaheemMitha systemd can definitely tell if a unit is running.

Faheem Mitha

@derobert I don't follow. apt-cache show what?

derobert

@FaheemMitha apt-cache show parallel | grep Conflicts

bugs.debian.org/cgi-bin/bugreport.cgi?bug=749355

Faheem Mitha

@derobert Oh. Why do they conflict? And moreutils does not present a conflict with parallel.

@derobert Oh, ok.

Why is the alternatives system not being used?

Ah

> Alternatives won't work, because the programs don't support compatible
command lines.

I didn't realise that was a requirement.

Hmm, old bug.

derobert

@FaheemMitha It's not...

But the problem is various packages & scripts just calling it as parallel.

Alternatives need to have some level of agreement on interface. Some have explicit specs (e.g., x-terminal-emulator is in policy, I believe). Others don't.

Pretty sure all the things that can provide editor don't agree on anything, except that they take a file name as an argument.

Faheem Mitha

5:17 PM

@derobert I see.

Abhishek Bhatia

10:10 PM

hi

I don't understand how the question is off-topic unix.stackexchange.com/questions/281164/…

I had posted on other sites a while ago.

derobert

@AbhishekBhatia Please read the off-topic comment you got... it's because of the multi-post

it gives you a link to the policy.

216

Q: Is cross-posting a question on multiple Stack Exchange sites permitted if the question is on-topic for each site?

It is possible to migrate a question from one Stack Exchange site to another by closing, but if I have a question that I think is on-topic for multiple Stack Exchange sites, is it OK to post it on both (multipost)? For example, I have a question that's earned me the tumbleweed badge on SO and I...

discussion faq questions etiquette cross-posting

this can be OK, so long as the question is tailored to each audience on the different sites and is materially different in each case. Just to be 100% clear, copy-pasting a question across sites with no changes is considered abusive behavor. — Jeff Atwood ♦ Jan 15 '11 at 3:51

... even if you go with the it can be OK sometimes, see that comment

Abhishek Bhatia

Thanks for the reply!

But the issue relates to kernel, thus it is more specfic to linux. Do you suggest I migrate it from ubuntu?

derobert

As for the actual question... I'm somewhat confused why it isn't working, as your xinput stuff seems to say it is.

You can ask for your AskUbuntu question to be migrated (or delete it, then ask for the one here to be reopened)

Or you can leave it there. Up to you.

although, it's not a mouse—it claims to report absolute position, not relative. More like a graphics tablet

Abhishek Bhatia

@derobert how did you figure that out?

derobert

@AbhishekBhatia Axis Labels (268): "Abs MT Position X" (428), "Abs MT Position Y" (429), "None" (0), "None" (0)

... it says Abs position, not Rel position

Abhishek Bhatia

10:25 PM

I tried to read from the device codepad.org/t3jpvZNj but the output I can't intrepret.

derobert

This is what a mouse looks like: Axis Labels (288): "Rel X" (160), "Rel Y" (161), "Rel Vert Wheel" (280)

@AbhishekBhatia I think that's just to grab raw data from it. Not sure exactly what that code is supposed to do...

Abhishek Bhatia

thanks for the information!

With a normal mouse the output should be something like this: orangecoat.com/how-to/…

derobert

I have to run... but your xinput test looks similar to what my mouse produces, except those values are huge. The mostion[0] and motion[1] I get correspond to positions (pixels) on screen.

Abhishek Bhatia

Once I get the absolute coordinates, I can normalize and move mouse through a script.

derobert

I would see if one of the corners of the device gives smaller numbers (with xinput test)... see if that part moves the pointer. If it does, I think you can probably fix it by feeding xinput a Coordinate Transformation Matrix.

(well, one that isn't the identity transform)

Anyway, have to go...

Abhishek Bhatia

10:33 PM

@derobert thanks so much! is there any way I get the maximum and minimum coordinate of that device for the transformation to be accurate?

derobert

11:57 PM

@AbhishekBhatia other than pressing your finger at all four corners? Not sure.

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